New generation antidepressant drugs, known as selective serotonin re-uptake inhibitors (SSRIs), increase the risk of gastrointestinal bleeding, finds research in this week's British Medical Journal.

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Canadian researchers monitored hospital admissions for gastrointestinal (GI) bleeding among almost 314,000 people, aged 65 and above, who had been prescribed antidepressants between 1992 and 1998.

Antidepressant drugs were grouped according to what extent they inhibited serotonin re-uptake.

There were 974 GI bleeds during the study.

The higher the inhibition of serotonin re-uptake, the higher was the risk of a bleed.

This was especially true of older patients, in whom the risk increased by over 10% for each more powerful grade of inhibitor drug. This was also true in those who had already had a bleed, in whom the risk increased by almost 10%.

For patients in their eighties, bleeding rates increased from 10.6 per 1000 person years for drugs with the lowest inhibition, to 14.7 with the highest.

This equalled an additional bleed for every 244 patients treated with the highest inhibiting drugs for a year.

The data also showed that the numbers of 80-year-olds prescribed SSRIs rose from 892 in 1992, to 11,179 in 1997.

Among patients who had had peptic ulcers, bleeding rates increased from over 28, to over 40 per 1000 person years.

This equated to an additional bleed for every 85 patients treated with the highest inhibiting drugs for a year.

The authors conclude that the extent to which antidepressants inhibit serotonin re-uptake should be considered before prescribing these drugs to very elderly patients or those who have had a bleed before.